1. Field of the Invention
The present invention relates to an ATM cell service apparatus for multiplexing an ATM cell from an ATM network into an N.A. (North America) new synchronous signal.
2. Description of the Related Art
Conventionally, there have been known a multiplexing device for accommodating an N.A. asynchronous communications network signal in an N.A. new synchronous network (SONET: synchronous optical network, refer to ANSI TI-105) and a new synchronous communications network according to the standards of the TTC (Telecommunication Technology Committee)(refer to JT-G707, JT-807, and JT-709), or a multiplexing device for accommodating an ATM (asynchronous transfer mode) cell in the N.A. asynchronous communications network (PDH: plesiochronous digital hierarchy network).
Recently, there are an N.A. asynchronous signal network (hereinafter referred to as a DSn network) and an N.A. new synchronous (SONET) signal network (hereinafter referred to a SONET) in an N.A. transmission network.
When the DSn network is connected to the SONET, a SONET optical transmission device is used. However, although a device for connecting a network (hereinafter referred to as a DS3 network) of a DS3 (44.736 Mbps) signal to a network (hereinafter referred to as a SONET STS-1) capable of performing a multiplexing/demultiplexing process in a SONET in an STS-1 (51.84 Mbps) signal unit has been put to practical use, a device for connecting an STM and ATM cell in a DS3 (44.736 Mbps) signal to a network capable of flexibly multiplexing/demultiplexing in a SONET in an STS-1 (51.84 Mbps) signal unit has not been put to practical use.
Only the SONET is described below, but the correspondence between the SONET and the TTC standards can be clearly understood.
Recently, there is a strong demand for a device capable of multiplexing/demultiplexing an ATM cell in an STS-1 unit while operating an N.A. asynchronous DS3 STM network, and entering the N.A. new SONET from the ATM network.
In this case, in a method of combining the conventional STM device with an ATM device, the entire device becomes large both in size and power consumption. In addition, in a method of generating an output AIS signal when an alarm signal is detected, the entire circuit becomes larger in size and power consumption if the conventional method used on the SONET side is adopted as is.
AISAlarm Indication SignalSONET specification termVCXOVoltage Controlled Xtal OscillatorGeneral term for a partsQuarts oscillator of whichthe frequency is variableby changing appliedvoltageDTPininput positive dataAbbreviation employed Inpresent patent applicationDTNininput negative dataAbbreviation employed inpresent patent application.BIT LEAK= memoryGeneral term for a functionBit by bit readjustment offluctuation in after-destaffdata timing. Called are-timing circuitPLCPPhysical Layer ConvergenceSONET specification termProcedureRDILLine Remote Defect IndicationSONET specification termISIDIDLE signal indicationSONET specification termName of a signal In LAPDdata-link using bits of DS3Cbit frameFEACFar End Alarm and ControlSONET specification term